The goal of this work is to determine what role interaction with actin may have in the regulation of phosphofructokinase. We will compare the effectiveness of skeletal muscle and smooth muscle actins in the binding and activation of phosphofructokinase. We will determine the effects of actin binding proteins - profilin, filamin, and DNase I -on the binding of the enzyme to F-actin. We will probe the erythrocyte to determine whether actin is responsible for the adsorption and activation of phosphofructokinase which occur in the presence of red blood cell membranes. Measurements of catalytic activity and of fluorescence polarization will demonstrate the macromolecular interactions and their effects.